CO 2 solubility Temperature: more soluble at lower temperatures. Salinity: more soluble in greater salinity. Pressure: more soluble under higher pressure.
Carbon dioxide buffering in the Ocean CO 2 enters ocean via diffusion and rapidly converts to HCO 3 - Reaction: CO 2 + CO 3 +H 2 O 2HCO 3 - As CO 2 in atmosphere rises the strength of ocean carbon uptake will weaken Adding more carbon and keeping it as CO 2 makes the ocean more acidic.
Dissolved Inorganic Carbon (DIC) CO 2 reacts to form other compounds of DIC. If in acidic solution: carbon in CO2 form If in basic solution: carbon mostly in carbonate form Ocean pH ~8 = Carbonate form
Ocean acidification By end of century, it is predicted that oceans surface-water DIC could decrease over 12% Carbonate ion concentration decrease almost 60% This would result in a pH drop in surface waters of 0.4 pH units
Impacts of anthropogenic CO 2 on Calcium Carbonate Aragonite and calcite undersaturation will occur at high latitudes when CO 2 values reach 1200 and 1900 µatm And at tropical/subtropical regions when CO 2 values reach 1700 and 2800 µatm Profound impacts on calcium carbonate shell-forming organisms
Alkalinity Determines pH and balances among forms of DIC The sum of cation charges minus the sum of anion charges Seawater is always positive, excess pos. charge This is balanced by carbonate system electrical neutrality CO 3 HCO 3 - CO 2
Carbonate Pump Organic productivity is also associated with calcium carbonate production. CaCO 3 precipitation decreases alkalinity by 2 units (via removal of double-charged Ca++) but the total CO 2 by only one unit (removal of CO 3 -) Due to dominance of alkalinity change, there is a net shift of carbon towards CO2 CO 3 -- HCO 3 - CO 2 Formation of CaCO 3 therefore increases surface water CO 2
Ocean and atmosphere in the North Atlantic Contribution of biological pump to anthropogenic carbon fluxes is very small everywhere except in high latitudes High latitudes biological pump’s contribution is ~20% of the solubility pump. The rate limiting step of anthropogenic CO2 uptake is ocean circulation and mixing.
Other Factors to consider Model shows as anthropogenic CO 2 increases there will be reduced uptake of CO 2 by oceans. Primarily as a result of weakening of collapse of thermohaline circulation El Niño events may be occurring more often as a result of increase anthropogenic CO 2